Sitophilus Granarius Research Articles

A very curious larder – Insects from post-medieval Skálholt, Iceland, and their implications for interpreting activity areas

Fossil insect assemblages from post-medieval Skálholt, the oldest episcopal see in Iceland, provide new information about indoor environments and the specific use of a structure which according to historical information was listed as a larder attached to the episcopal school. The assemblages recovered also provide information on the background fauna which comprises of species related to turves, used for building construction and indicating storage of peat. In addition to the introduced Sitophilus granarius, the granary weevil, a new pest, Callosobruchus maculatus which is a pan-tropical and subtropical field and storage pest of legumes, and a rarely introduced species in Iceland even today, were also recovered from the site. In view of the nature of the assemblages, these were probably accidental introductions into the room, perhaps in faeces. The historical record provides information about the life history and events at Skálholt and data about school supplies including imports of stored products to Iceland during this period. In addition, the high numbers of sheep keds, Melophagus ovinus, combined with high numbers of human lice, Pediculus humanus, point to the washing of wool and clothing in urine to get rid of ectoparasites. Intra-site comparisons and a review of all Icelandic archaeological sites suggest a clear correlation between the presence of ectoparasites and wool preparation and cleaning. The results from Skálholt clearly show that rooms and specific spaces in post-medieval buildings could have multiple functions, not only the one assigned to them in the historical record.

Behaviour desorption study of the essential oil of Cedrus atlantica in a porous clay versus insecticidal activity against Sitophilus granarius: explanation of the phenomenon by statistical studies

Substances of natural origin and more particularly essential oils currently represent an alternative solution in the fight for the protection of stored foodstuffs. The way to use these essential oils and the storage conditions remain the main handicap in dealing with this subject. This article develops the use of porous supports as a medium for the study of the behavior of essential oils with respect to insecticidal activities. The process relates to the fixing and/or grafting of essential oils in porous clay media in a well-defined geometric form included in the storage methods. The study of transfers of the essential oil of Cedrus atlantica in a porous clay medium in the case of desorption was made by analytical and numerical models of diffusion process, to know the behavior of the oil and to determine some physical parameters (diffusivity Dz, activation energy Ea, evaporation rate F and constant of evaporation K) which explain the mechanisms involved and to try to exploit them in parallel with the insecticidal activities against of Sitophilus granarius the main cereal pest by statistical approaches such as: design of experiments and principal component analysis.

Combined effects of Azadirachtin and Citrus limonum essential oil against Sitophilus granarius: Toxicity and Biological Activities

Combined effects of Azadirachtin and Citrus limonum essential oil against Sitophilus granarius: Toxicity and Biological Activities

Procjena štete od žižaka (Sitophilus granarius L. i Sitophilus zeamais Motsch.) na različitim hibridima kukuruza

Storage pests are pests adapted to living indoors, where their entire life cycle occurs on stored agricultural products. Nowadays, insects within storage facilities are the main problem in the storage process. Storage systems such as silos, warehouses, and containers are perfect habitats for insects that feed on stored food because they are protected from weather extremes, have unrestricted access to large food sources, and can live continuously for long periods of time. The objective of this study was to determine the intensity of damage by granary (Sitophilus granarius L.) and maize (Sitophilus zeamais Motsch.) weevils on field maize and popcorn and their biological potential over 20 weeks of the storage process. During the study, physical properties of maize (weight, hectolitre weight, moisture and sample weight) and changes in population density of weevils were measured. The results showed differential susceptibility of maize hybrids to weevil feeding. No differences were found between weevil species in terms of the damage they caused. Popcorn does not favor weevil feeding, resulting in low grain damage and high mortality rates for both weevil species. In contrast to popcorn, field corn favors both weevil feeding and weevil reproductive potential, ultimately decreasing grain mass and quality and making it unsuitable for human and livestock consumption. More susceptible field maize can be selected for shorter storage time and thus faster delivery to market.

Ответственность зерновых долгоносиков в загрязнении зерна мочевой кислотой

Experimental studies have established a mathematical dependence of the uric acid content in wheat grain on the density of its Sitophilus granarius.

Bazı bitki ektraktlarının Sitophilus granarius (Linnaeus, 1758) (Coleoptera: Curculionidae) ve Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) üzerindeki insektisidal ve davranışsal etkileri

Depolanmış ürünlerdeki böceklerle mücadele oldukça önemlidir. Sitophilus granarius (Linnaeus, 1758) (Coleoptera: Curculionidae) ve Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidea) depolanmış ürünlerde zarar meydana getiren önemli iki zararlı böcek türüdür. Depolanmış ürünlerdeki zararlılarla mücadelede kullanılabilecek alternatif ilaçlara ise her geçen gün ihtiyaç artmaktadır. Bu çalışmada, Achillea phrygia Boiss. et Bal. (Compositae), Prangos ferulacea (L.) Lindl. (Apiaceae) ve Salvia wiedemannii Boiss. (Lamiaceae) bitkilerinden elde edilen bitki ekstraktlarının, S. granarius ve T. castaneum ile mücadelede kullanılabilirlikleri araştırılmıştır. 72 saat sonunda, S. garanarius üzerinde test edilen bitkiler arasında en yüksek kontak aktiviteyi sırasıyla %74 ile P. ferulaceae hekzan, %71 ile A. phrygia methanol ekstraktı göstermiştir. T. castaneum üzerinde en yüksek aktiviteyi ise 72 saat sonunda %42 ile A. phrygia etil asetat ekstraktı göstermiştir. Bitki ekstraktları ile yapılan davranışsal etki çalışmalarında ise S. granarius üzerindeki en yüksek repellent aktivite 24. saat sonunda P. ferulaceae etil asetat ekstraktından (%52) elde edilmiştir. Bitki ekstraktlarının tamamı T. castaneum üzerinde yüksek oranda repellent etki göstermiştir.

Evaluation of biological activities of two essential oils as a safe environmental bioinsecticides: case of Eucalyptus globulus and Rosmarinus officinalis

All works of this article were conducted to investigate chemical composition and insecticidal and antimicrobial properties of Eucalyptus globulus and Rosmarinus officinalis essential oils isolated by hydro-distillation of its aerial parts. Analysis of the essential oils on the basis of gas chromatography and mass spectrometry (GC/FID and GC/MS) revealed the presence of 82 organic volatiles representing 98.63% of the total constituents of Eucalyptus globulus and the presence of 45 organic volatiles representing 98.53% of the total constituents of Rosmarinus officinalis. The major compounds for Eucalyptus globulus were estragole (28.14%), terpinolene (7.12%), 1,4-hexadiene-5-methyl-3-(1-methylethylidene) (7.01%), linalool (5.54%) and furfural (4.66%) and for Rosmarinus officinalis were (-)-camphor (31.16%) and ß-caryophyllene (18.55%), 3,4-dimethyl-(Z,Z)-2,4-Hexadiene (9.08%), ?-fenchene (4.67%), cis-verbenone (4.33%) and Bornyl acetate (3.4%). The efficacy of the two essential oils was evaluated on the insect pests Sitophilus granarius of wheat and was remarkable with lethal doses of 50% tending towards 1 µL·cm–3. The broth microdilution method as a complementary test was conducted to test the antimicrobial activity of the essential oil against: Staphylococcus aureus, Enterococcus faecium, Listeria monocytogenes, Bacillus subtilis, Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa and Candida albicans, further for the two oils of shows promising activity against all strains.

Knockdown-Mortality Responses of Six Stored-Product Beetle Species on Different Surfaces Treated With Thiamethoxam, Using a Standardized Lethality Index

Bioassays were conducted to evaluate the effectiveness of thiamethoxam in different surfaces, against six stored-grain insects, Sitophilus granarius (L.) (Coleoptera: Curculionidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae). Six different surfaces (concrete, plywood, galvanized steel, linen, plastic, and ceramic tile) treated with thiamethoxam at 0.05 and 0.1 mg/cm2 were used as substrate for adult exposure. Knockdown was recorded after 1, 3, and 7 d of exposure to the treated surface, in order to calculate a Standardized Lethality Index (SLI). Knockdown counts were ranked from '0' to '4', with '0' representing adult insects 'moved generally' and '4' representing dead insects. Based on the results, insect knockdown seems leading to mortality than to recovery and the SLI ranking of the target species according to their susceptibility to thiamethoxam showed that S. granarius being more susceptible and decreasing susceptibility in an order of S. oryzae > T. castaneum ≥ O. surinamenis ≥ C. ferrugineus ≥ T. confusum. In general, among the surfaces, thiamethoxam efficacy was lower on linen, wooden, and concrete surfaces, as compared to metallic and plastic surfaces. Nevertheless, at the end of 7-d exposure, all surfaces equally affected thiamethoxam toxicity.

CHEMICAL STUDY AND EVALUATION OF INSECTICAL PROPERTIES OF AFRICAN LIPPIA CITRIODORA ESSENTIAL OIL

The main objective of this study is to highlight the chemical composition, the insecticidal and the antibacterial activities of essential oil of Lippia citriodora growing spontaneously in central Morocco, particularly in Beni Mellal. After extracting the essential oil by a clevenger type distiller from the aerial parts, all constituents were analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Their chemical composition of chemotype revealed the presence of 45 compounds in the essential oil, which has Geranial as the major constituent with a content of approximately (35.45%), followed by Neral (26.11%) and Limonene (14.06%), with a total percentage of (75.62%). The insecticidal activities were carried out against three weevils:Sitophilus granarius, Sitophilus oryzae and Sitophilus zeamais, the results of this test to show a very important activity during 24 hours of the treatments confirmed by the values of LD50 and LD90 which tend towards 0, or this activity was probably due to the major constituents. The bacterial power was studied in vitro against gram-positive bacteria: Bacillus cereus (CECT 193) and Listeria monocytogenes (CECT 4032), gram-negative bacteria: Yersinia enterocolitica (CECT 9144), Pseudomonas aeruginosa (CECT 116) and Staphylococcus aureus (CECT 239), the results of this tests made it possible to quantitatively assess the bacterial power by looking for minimum MIC inhibitory concentrations and minimum MBC bactericidal concentrations, which have a varying activity depending on the strain tested.

INSECTICIDAL EFFECT OF THREE ESSENTIAL OILS AND BEAUVERICIN NANO GEL ON SITOPHILUS ORYZAE AND SITOPHILUS GRANARIUS (COLEOPTERA :CURCULIONIDAE)

Sitophilus oryzae and Sitophilus granarius (Coleoptera :Curculionidae) harmful insects cause a damages to stored product seeds. These pests controlled by chemical materials which pollute the environments. Essential oils are a natural compound used as insecticide to a lot of pests. In our research we controlled these pests by essential oils, Cinnamomum zeylancium, Zingiber officinale, Cuminum cyminum and Beauvericin nano gel 2%. Results showed that, the LC50s of S. Oryzae were 38, 44, 151 and 18 ppm for Beauvericin nano gel 2% C. zeylancium, C. cyminum and Z. officinale, respectively. Also LC50s for S. granarius obtained by the corresponding treatments were, 41, 144, 11and 29ppm. The accumulative of S. oryzae significantly increased after 48 (H) by 2.8 fold after application of Cinnamomum zeylancium oil. When Zingiber officinale Oil applications the accumulative mortality increased by 3,3fold. The Beauvericin nano gel 2% showed that the accumulative increased by increasing the exposure time.Cinnamomum zeylancium showed a higher effect on the wheat weevil S. granarius, where the accumulative mortality recorded 91 after 48 (H). The lower accumulative mortality after Beauvericin nano gel 2%, recorded 38 after 48(H). The repellency test showed that, the highest repellant found among the Beauvericin nano gel 2% treatments. Data presented show that the persistence effectiveness of oil significantly decreased by increasing the storage time. The potential of the insecticidal oils was high after 45 days of storage, against S. oryzae and S. granarius. The potential of the insecticidal effect of oil recorded the lowest percentage at the end of storage after 100 days to both S. oryzae and S. granarius.

Efficacy of three vegetal powders against Sitophilus granarius in stored wheat and the evaluation of their effect on grain parameters

ABSTRACT Doses of 5,10,15, 20 and 25 g of three plant powders,Atractylisgummifera rhizome (AGRP), Daphne gnidium (DGP) and Thapsiagarganica (TGP), were added to 100 g of durum wheat to study their insecticidal effect and ability to preserve the agronomic characteristics of stored grains against the attacks of Sitophilus granaries durum wheat pest overa storage period of 6 months inTiaret district. Algeria. Our results showed that AGRP and DGPcaused 100% mortality, andTGP induced 90%. LD50 and LD90 values of 7.24, 8.51, 10.71 and12.88, 15.48, 26.91 g/100 g of wheat were recorded respectively with AGRP, DGP and TGP. We observed a highly significant reduction in the number of eggs laid and offspring emergence, a decrease in weight loss and grain damage, anda high germination percentage in the treated grains. The three powders represent a promising alternative against Sitophilusgranarius.

Effect of Citrus limonum essential oil against granary weevil, Sitophilus granarius and its chemical composition, biological activities and energy reserves

Stored grains could lose substantially their nutritional quality, and consequently its value, between storage and consummation because of insect’s infestation. One of the most frequent pests of wheat is the grain weevil (Sitophilus granarius L.). Cleverly hidden, the immature stages of this destructive pest are very difficult to identify. Protecting stored grains has become an agricultural challenge. In the present study, the essential oil (EO) distillated from Citrus limonum (L.) (Burm. F., 1768) and analyzed by gas chromatography-mass spectrometry (GC-MS) revealed the presence of 47 compounds with (Z)-citral (30.74%), dl-limonene (19.81%) and geranyl propionate (16.28%) as major components. In a second series of experiment, its fumigant (using filter paper), repellent (by semi circles joined discs) and residual (persistent insecticidal activity) activities were examined against Sitophilus granarius (L.) adults. The total nutrition (carbohydrates and lipids) depletion index (NDI) was also calculated. Residual toxicity and repellency of EO were demonstrated after fumigation against S. granarius with a dose-response relationship. The effectiveness of EO was exposure time dependent and its residual activity persisted up to 30 h following mortality. Moreover, data showed that treatment of S. granarius adults had adverse effects on the depletion of their energy reserves. C. limonum EO declined the lipid and carbohydrate contents in adults. Obtained data prove that botanical essential oils could be considered as potent biorational alternatives to synthetic insecticides for pest control of stored products in a sustainable manner.

Screening stored wheat beetles for reproductive parasitic endosymbionts in central Turkey

Stored-product pest insects cause significant loss in stored wheat worldwide. In Turkey, an important wheat producer and historic centre of wheat domestication, almost 60 stored-product pest insects have been reported so far, most of them being coleopteran species. Using reproductive parasitic endosymbionts (RPEs) is a promising recent approach among control methods alternative to insecticides. For planning and studying pest management with these bacteria, first of all, their presence in the natural pest populations should be investigated. The present study focused on screening the RPEs in Central Anatolian stored wheat pests. We collected pests in granaries in Kırşehir province and identified 10 coleopteran species both morphologically and genetically; namely, Ahasverus advena, Cryptolestes ferrugineus, C. pusillus, Carpophilus obsoletus, Oryzaephilus surinamensis, Rhyzopertha dominica, Sitophilus granarius, S. oryzae, S. zeamais, and Tribolium castaneum. In these pests, we screened the most commonly studied RPEs worldwide, Arsenophonus, Cardinium, Fritschea, Hamiltonella, Rickettsia, Spiroplasma, and Wolbachia, by using specific genetic primers. As a result, we detected RPE presence in almost all sampling localities visited. The RPEs that we found were Rickettsia, Spiroplasma, and Wolbachia. We found no infection caused by Arsenophonus, Cardinium, Fritschea, nor Hamiltonella. Rickettsia presence was only in S. granarius populations, whereas Spiroplasma and Wolbachia presence were not species specific. 22% of all sampled beetle individuals were Wolbachia positive. The highest detection rate per granary was that of Spiroplasma (80%). Wolbachia and Spiroplasma were the most frequently detected RPEs per insect species. We also found several cases of coinfections. This study is the first attempt to screen stored-product pests for seven RPEs together.

Chemical composition and insecticidal, repellent and antifungal activities of essential oil of Mentha rotundifolia (L.) from Algeria

The biological struggle by the use of the natural substances that have a pesticide effect may be an alternative to harmful chemicals; among these natural substances are the extracts of aromatic plants especially essential oils. The present work aims to highlight the fungicidal and insecticidal effect of the essential oil (EO), of an aromatic plant Mentha rotundifolia, against respectively, a phytopathogenic mold (Fusarium culmorum) and the adults of two pests (Sitophilus granarius and Tribolium confusum) of stored grains. The evaluation of the chemical composition of the EO was carried out by gas chromatography coupled to mass spectrometry (GC/MS). The analysis made it possible to identify 27 compounds, which corresponds to 97.93 % of the totality of the oil of which the majority compounds are: Piperitenone oxide 35.49 ± 0.08, Caryophyllene oxide 35.27 ± 0.13 and cis-Cinerolone 10.95 ± 0.05. The bioassays to assess the EO toxicity towards the pest insects revealed a very high effect, which increases significantly with the dose and the time of exposure. Similarly, the test for the repellent effect shows that this extract is a powerful insect repellent. In addition, we found that both the liquid and vapor phases of the EO present an inhibitory effect of the growth of the fungal strain. In the light of the results obtained, the plant studied is promising as a source of natural pesticides and lends itself well to research in the field of pest control using biochemical alternatives.

Persistence of diatomaceous earth, SilicoSec® against three stored grain beetles

The persistence of a commercially available diatomaceous earth (DE) formulation (SilicoSec®) against Sitophilus granarius, Rhyzopertha dominica and Tribolium confusum on wheat at four dose rates (500–2000 mg/kg) during a 360-day period of storage was assessed. Mortality of S. granarius were 76.0, 88.4, 93.2 and 95.6% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 31.5%,71.3, 87.2 and 96.8 at 12 months with the same dosage. Mortality of R. dominica were 48.0, 79.6, 86.4 and 90.0% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 82.7, 95.2, 98.0 and 98.8% at 12 months with the same dosage. Mortality of T. confusum were 82.1, 96.8, 98.8 and 100.0% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 32.8, 99.6, 100.0 and 100.0% at 12 months with the same dosage. The increase in mortalities obtained from 1500 to 2000 mg/kg for each of the three species were mostly insignificant at 28 d exposure. Therefore, wheat treated with SilicoSec® at a dosage of 1500 mg/kg could be satisfactorily protected against S. granarius, T. confusum and R. dominica for a year.

Insecticidal and behavioral effects of some plant essential oils against Sitophilus granarius L. and Tribolium castaneum (Herbst)

Insecticidal, repellent and fumigant activities of Rosemary [Rosmarinus officinalis (Lamiaceae)], Daphne [Laurus nobilis (Lauraceae)], Echinacea (Echinacea purpurea (Asteraceae), Marjoram [Origanum majorana (Lamiaceae)], Basil [Ocimum basilicum (Lamiaceae)] and Fennel [Foeniculum vulgare (Apiaceae)] extracts were tested against Sitophilus granarius (Col.: Curculionidae) and Tribolium castaneum (Col.: Tenebrionidae) under laboratory conditions. The composition of essential oils extracted from the plants was also determined. Eucalyptol and Terpinyl acetate were the main components of Daphne oil. Similarly, the main components of Basil oil were Methyl cinnamate, Linalool and Eucalyptol, whereas Camphor and Eucalyptol were the main constituents of Rosemary oil. Likely, γ-Terpinene and β-Terpineol were the main components of Marjoram oil, while Estragole was the main component in Fennel oil. The β-Cubebene and Caryophyllene were the main components of Echinacea oil. Echinacea and Basil oils exhibited high contact toxicity against S. granarius. Basil oil caused 99.59% mortality of S. granarius 24 h after application, whereas Echinacea oil caused 99.59% mortality 72 h after application. In single-dose fumigant toxicity assays, Rosemary oil exhibited 58.41% fumigant activity against S. granarius after 24 h, whereas Fennel oil indicated 100% fumigant toxicity against T. castaneum. All essential oils showed repellent effects against both the pests. The essential oils caused 34.12–95.29% decrease in the progeny production of F1 generation of T. castaneum, while the decrease in the F1 generation of S. granarius ranged between 84.27 and 98.88%. It is concluded that essential oils of Fennel, Rosemary, Echinacea and Basil could potentially be used for the control of studied stored grain pests.

Efficacy of visual evaluation of insect-damaged kernels of malting barley by Sitophilus granarius from various observation perspectives

Although there is growing evidence that arthropod detection methods are not sensitive enough to meet current quality demands, few adequate validations are available for the detection of insect-damaged kernels (IDK- quality parameter). Therefore the aims of this work were to (i) describe categories of exit holes of Sitophilus granarius (L.) in terms of their location on the grain surface; (ii) analyse spatial distribution of exit holes on kernels of three varieties of malting barley; (iii) analyse the sensitivity of visual laboratory methods for IDK detection, and (iv) test if the turning effect of automatic shaking can increase damage visibility from the upper-view perspective of an inspector. Six topological categorises of exit holes were described and photo-documented. It was found that the relative distribution of exit holes on the kernel surface was in decreasing order from lateral, brush, ventral or dorsal (depending on variety), subapical, to germ area. The ventral and dorsal exit holes were significantly bigger than the apical exit holes. It was found that distribution patterns of exit holes on kernels affected their proportional visibility from various observation perspectives. Only 50% of lateral or dorsal exit holes was visible from top or crease views, respectively. The most effective was the side (brush end) view perspective, with visibility of up to 90% of exit holes. Although the shaking effect was statistically significant, it only increased the efficacy of upper view detection perspective from 54% to 58%. This is the first study showing that the inspector upper view of inspected grain samples (without grain rotation) poses a risk of underestimating actual insect-damaged kernels by 50%. Thus, advanced methods that are independent of observation perspectives (X-ray, NIRS, etc.) should be promoted for routine use in commercial laboratories, despite higher cost.

Comparison of efficacy of nitric oxide fumigation under nitrogen and carbon dioxide atmospheres in controlling granary weevil (Sitophilus granaries) and confused flour beetle (Tribolium confusum)

Nitric oxide (NO) was a recently discovered fumigant for postharvest pest control. Because NO reacts with oxygen (O2) spontaneously to form nitrogen dioxide (NO2), NO fumigation must be conducted under ultralow oxygen (ULO) atmospheres to preserve NO and nitrogen (N2) has been used to establish ULO atmospheres in NO fumigation studies in the past. However, carbon dioxide (CO2) can also be used to ULO atmospheres and CO2 fumigation was also reported to be effective in controlling certain insect pests and enhancing toxicity of some fumigants. In the present study, NO fumigations under ULO conditions established with N2 and CO2 were compared for effects against granary weevil, Sitophilus granaries, and confused flour beetle, Tribolium confusum. All life stages of the two insects were subjected to 12 h fumigation treatments with 0.5–1.0% NO at 25 °C under ULO established with CO2 (NO–CO2 treatments) and N2 (NO–N2 treatments). The most tolerant life stage for each species in each fumigation treatment was then fumigated with NO for 24 h fumigation at 25 °C to determine an effective treatment. There were no significant differences in mortalities of adults, larvae, and pupae at all NO concentrations between ULO conditions established with CO2 and N2 for either insect. NO–CO2 was, however, significantly less effective than NO–N2 against eggs of both species. Granary weevil pupae and confused flour beetle eggs were the most tolerant stages for each respective species to NO fumigation: >99% mortality of granary weevil pupae and confused flour beetle eggs were, however, achieved in the 24 h fumigation with 2% and 1% NO, respectively. This study showed that CO2 can be used to establish ULO atmospheres for NO fumigation, but did not significantly contribute to insect mortality.

Biological Activity of Humulus Lupulus (L.) Essential Oil and Its Main Components Against Sitophilus granarius (L.).

Besides its use in the brewing industry, hop cones appear as a powerful source of biologically active compounds, already checked for their putative anticancer, antimicrobial, and other bioactivities. Conversely, hop use in pest control remains to date under-investigated. Therefore, the biological activity of hop essential oil (EO) and its main constituents was investigated here against Sitophilus granarius. Adult contact toxicity was found 24 h after treatment with hop EO (LD50/LD90 13.30/40.23 µg/adult), and its three most abundant components, α-humulene, β-myrcene, and β-caryophyllene (LD50/LD90 41.87/73.51, 75.91/126.05, and 138.51/241.27 µg/adult, respectively); negligible variations at 48 h, except for α-humulene (LD50/LD90 26.83/49.49 µg/adult), were found. The fumigant toxicity of the EO and terpenes was also checked: in the absence of wheat grains, β-myrcene showed the highest inhalation toxicity (LC50/LC90 72.78/116.92 mg/L air), whereas α-humulene, β-caryophyllene, and the EO induced similar values (LC50/LC90 about 130/200 mg/L air); with the exception for EO, the wheat presence increased (30–50%) LC50/LC90 values. Moreover, EO and terpenes were perceived by insect antennae and elicited repellent activity. Only β-caryophyllene showed an anticholinesterase effect, this suggesting that different mechanisms of action should be responsible for hop EO toxicity. Therefore, hop EO appears suitable for developing control means against this pest.

Effect of Volatile Compounds of the Entomopathogenic Fungi Beauveria bassiana (Bals.-Criv.) Vuill. and Lecanicillium muscarium R. Zare et W. Gams on the Behavior of Sitophilus granarius (L.) (Coleoptera, Dryophthoridae) and Evaluation of the Virulence of Different Strains of These Fungi

Adult granary weevils feeding on grain responded selectively to the volatile compounds of different strains of the entomopathogenic fungi Beauveria bassiana and Lecanicillium muscarium. The mycelium of B. bassiana strains had a repellent effect or a neutral effect with a tendency toward repellency. The response to L. muscarium strains varied from weak repellent (G-033) and neutral (Vl 49) to attractive one (Vl 21). Beauveria bassiana strain Bb 17 showed the highest virulence after beetles were sprayed with conidial suspension containing 1.0 × 108 spores / ml: the mortality of the beetles on the 7th day reached 74% with extensive mycelial growth over the dead beetles, LT50 was 5.6 days for this strain and 23 days for strain Bb 13. The L. muscarium strains showed low virulence, with the exception of strain G-033 (LT50 15.3 days), and they also formed mycelium on the dead insects. The granary weevil response should be considered when assessing the potential of entomopathogenic fungi. Beauveria bassiana strain Bb 17 was selected as a promising pest control agent, since neutral reaction of the granary weevil to its mycelium facilitates the spreading of fungal infection.